C/2017 T2 (PANSTARRS)

C/2017 T2 (PANSTARRS) is an Oort cloud comet discovered on 2 October 2017 when it was 9.2 AU (1.38 billion km) from the Sun. The closest approach to Earth was on 28 December 2019 at a distance of 1.52 AU (227 million km). It came to perihelion (closest approach to the Sun) on 4 May 2020[2] when it was safe from disintegration at 1.6 AU from the Sun. (Mars is also roughly 1.6 AU from the Sun.)

C/2017 T2 (PANSTARRS)

C/2017 T2 (right) passing near Messier 81 and Messier 82 on May 22, 2020
Discovery
Discovered by	Pan-STARRS
Discovery date	2 October 2017
Orbital characteristics ^A
Epoch	2458756.5 (30 Sept 2019)
Observation arc	2.68 yr
Orbit type	Oort cloud
Aphelion	~74000 AU (inbound)[1] ~3000 AU (outbound)
Perihelion	1.6150 AU
Eccentricity	0.99971
Orbital period	~7 million years (inbound)[1] ~58000 years (outbound)
Inclination	57.232°
Earth MOID	1.2 AU (180 million km; 470 LD)
Jupiter MOID	0.99 AU (148 million km; 390 LD)
Last perihelion	4 May 2020[2]

Comet C/2017 T2 (PANSTARRS) has brightened to apparent magnitude 8 and is visible with 50mm binoculars.[3][4] In early June 2020 the comet was near the magnitude 1.8 star Dubhe in Ursa Major.

JPL Horizons using an epoch 1950 orbit solution models that C/2017 T2 took millions of years to come from the Oort cloud at a distance of roughly 74,000 AU (1.2 ly).[1]

References

1. JPL Horizons barycentric solution for epoch 1950 (before entering planetary region)
   Goto JPL Horizons
   Ephemeris Type: Orbital Elements
   Center: @0 (Solar System Barycenter)
   Time Span: 1950-01-01 to 2050-01-01 and Step Size: 100 years
   1950-Jan-01 is "PR= 2.58E+09 / 365.25 days" = ~7 million years AND "AD= 7.38E+04" = ~74000 AU @ Aphelion
2. "JPL Small-Body Database Browser: C/2017 T2 (PANSTARRS)". Jet Propulsion Laboratory. Retrieved 27 May 2020.
3. "Comet Observation database (COBS)". Retrieved 27 May 2020. "C/2017 T2 (PANSTARRS) plot"
4. Seiichi Yoshida. "C/2017 T2 ( PanSTARRS )". Retrieved 27 May 2020.